Printing accessory



Aug. 27, 1957 .1.- WAN..-

B. S. CROSS ETAL PRINTING ACCESSORY Filed Jan. l5, 194'? United StatesPatent C M' PRINTING ACCESSRY Bert S. Cross and Melvin lL. Gebhard, St.Paul, Minn., p assignors to Minnesota Mining & Manufacturing Qompany,St. Paul, Minn., a corporation of Delaware Application .ianuary 13,1947, Serial No. 721,770

1 Claim. (Cl. 154-545) This invention relates to printing accessoriesand particularly to draw sheets, blankets or the top cover of impressioncylinders employed in letterpress printing. The invention has particularutility in perfecting presses, which include the high speed rotarypresses upon which metropolitan newspapers are printed. In letterpressprinting, the printing pressure is developed by compression of the paperto be printed upon, held between rigid surfaces which are maintainedapart at predetermined distances. Pressure is required to transfer inksatisfactorily from the printing surface to the paper to be printed. Inperfecting presses, this pressure is partially supplied by packingsecured to the circumference of the impression cylinders of the press.The packing on the impression cylinder of rotary newspaper presses isapproximately .160 inch to .190 inch in thickness. It usually comprisesunderpacking which is tightly wrapped around the impression cylindermaking up the bulk of the clearance and a top cover, usually called adraw sheet or blanket. Y

In newspaper rotary presses the packing employed usually is one of twotypes. For example, a heavy blanket comprising three or more layers ofrubber and fabric is secured over a lamination of rubber or corkunderpacking. The blanket is usually .080 inch to .092 inch thick.Another packing for newspaper rotary presses includes two layers of corkor rubber as the underpacking and a top cover, called a draw sheetconsisting of a highly vulcanized synthetic rubber laminated to fabric.In this construction the draw sheets are thinner than the blanketspreviously mentioned and are from .024 inch to .030 inch thick. Afurther draw sheet comprises cloth having a coating of compressiblerubber or resin cups.

Blankets and draw sheets of the type described do not prevent or reduceoffset in any substantial measure. Offset has been described as thetendency of undried ink to transfer from a freshly printed sheet to anyother surface with which it comes in contact, particularly the blanket,draw sheet or tympan sheet on the second impression cylinder, and toretransfer back to the' printed sheet. Rotary perfecting presses includetwo units or couples and each unit is composed of a plate cylinder andan impression cylinder. In order to print upon both sides of the paperin a single printing operation, in one unit the plate cylinder is underthe impression cylinder and in the other unit the plate cylinder is overthe impression cylinder and the paper web moves rapidly from oneprinting couple to the other. The operation of rotary presses isconducted so rapidly that the ink applied to the paper in the first pairof cylinders does not dry before the other surface of the paper web isprinted in the second pair of cylinders. In modern newspaper presses inwhich the paper web may travel at speeds of 1500 feet per minute, only afraction of a second intervenes between the first and second printingimpressions. Since newspaper printing inks dry by absorption of thevehicle into the paper, it is obviously impossible to dry thepink inasistan Patented Aug. 27, 1957 the short time interval between the rstand second printings of the two sides of the web. As a result some ofthe wet ink from the tirst impression printing is transferred or offsetOnto the surface of the blanket or draw sheet on the second impressioncylinders. Wet ink accumulates rapidly on the surface of the top sheetof the second impression cylinder and after a number of printingimpressions a state of equilibrium is reached in which the ink isretransferred from the top cover surface to the already printed side ofthe web in the pattern of the pressure applied during the secondprinting. Thus the quality of the first impression printing is impaired.For example, type matter of the second impression printing may appear onhalf tone reproductions of the first impression printing and mars theappearance of the half tone. The quality of the iirst impressionprinting is further damaged by the fact that it is impossible to keepthel web tracking accurately so that each printed page will registerexactly with the ink oifset onto the top cover by previous impressions.As a result substantially the entire circumference of the draw sheet orblanket becomes lightly coated with wet ink.

This problem is further aggravated in newspaper presses, which do notemploy make-ready, due to the fact that time is of the essence inproducing newspapers. Makeready is the expression employed for alteringthe surface of the support for the material to be printed in order tocompensate for mechanical inaccuracies in the printing surfaces and toobtain increased printing pressurev for such areas as may require it.Since it is a custom job and requires several proof printings, it isobviously timeconsuming and costly, and hence is not employed inYnewspaper printing. Thus in order to compensate for ther inaccuracies inthe printing surface and in order to print low areas in the printingsurface, a resilient packing is required on the impression cylinders ofnewspaper rotary presses by the nature of the hard squeeze which is im-`parted to print the entire stereotype. l Y

Differences of up to .006 inch in the surface level is frequent onstereotype faces. Thus the absence of make-i ready tends to aggravateoffset and to emphasizethe need of a hard-surfaced packing resilientlysupported.

Furthermore, smearing or blurring of the rst impression printingfrequently occurs due to slippage of the paper web between the cylindersof the second printing couple. This may be caused if the plate andimpression cylinders are not of the same circumference or by movement ofthe stereotypes on the plate cylinders by centrifugal force at normalhigh speeds of rotation. The problem is frequently aggravated, when softpacking is employed, by slight piling up of the draw sheet in advance ofthe linear width of the web being printed.

Various expedients have been unsuccessfully tried by the printingindustry over a period of many years to overcome the problem of firstimpression oifset. For example, liquids and powders have been sprayedupon the freshly printed web to facilitate the drying of the ink or tocover it during its travel over the second impression cylinder. Specialdryers have been incorporated in inks and the ink has been heated tohasten the drying. Modifying the tension on the web as it is drawnthrough the press also proved to be unsuccessful. The use of variousmaterials having smooth, non-porous or ink-repellent surfaces, such ascellophane or mercury-coated materials likewise were unsuccessful inthat they did not withstand the hard usage of long printing runs. Steeland hard rubber surfaces on the impression cylinder did not provide theanswer as they did not have the necessary resiliency to absorb highspots on the printing surfacey to permit the remainder of the type tomake an adequate printing contact with the paper web being printed.

Since it takes time to replace the draw sheet or blanket on theimpression cylinder, as it is retained thereon by c lamps or pins and areel member, and as previously mentioned, time is of the essenceingrnodern newspaper and magazine production, it is essential that thetop lsheet or blanket be exceedingly strong and durable. In fact asatisfactory draw sheet or blanket for newsprint presses must last forapproximately l to 15 million printing impressions under high speedoperation, in which as high as 6 revolutions or printing impressions persecond may be made. l

It is also necessary that the top cover be oil-resistant in orer toavoid swelling of the draw sheet from the ink vehicle or from cleaners,which would result in inaccurate pinting and premature disintegration ofthe top cover s eet.

We have found that a blanket or draw sheet having highly satisfactoryproperties,` particularly in respect to very material reduction of rstimpression offset, may be provided by presenting a hard, discontinuous,planar surface supported by a durable and resilient backing material. A`single layer of minute spherical or spheroidal bodies of substantiallyuniform diameter have been found to have the requisite strength,hardness and surface characteristics of a draw sheet or blanket and toproduce even printing on presses which do not employ make-ready. Thesebodies are securely bonded individually to a strong, resilient andflexible backing, leaving half or somewhat less than half the diameterof each body projecting for contact with the freshly printed web. Thebacking comprises a tough, resilient shear-resistant fabric or paper. Anadhesive is employed which is not only resilient and resistant to impactbut also has strong adhesion to the spherical bodies and to the backing.The spherical beads or bodies are submerged in the adhesive to a depthof not less than half their diameter in order that a socket coveringfrom 50 to 75 percent of the bead area is formed by the adhesive coat. Asheet adapted to withstand the rough usage as a top cover on theimpression cylinder of newspaper presses is obtained if the beads aresubmerged to 'about 60 percent of their surface in the adhesive.

To obtain most satisfactory results in newspaper presses, the improveddraw sheet or blanket preferably has a resilient or cushioning layerinterposed between the fabric backing and the beads. As will be broughtout in greater detail, the desired resilience may be obtained byemploying a thicker layer of adhesive, or, as isY preferred, a separatecushioning layer or layers may be employed, intermediate the beads andthe fabric backing'or upon the outer surface of the fabric backing.

C Glass beads provide the required hard face necessary to obtainaccurate printing. For example, beads formed from a lime soda glass,such as that commonly used in the construction of glass containers andwindow panes are very suitable. However, since the opticalcharacteristics of the material are not involved, the beads maybe formedfrom iron, steel or other metals or alloys, or from ceramic material,rubber or synthetic resins having the required hardness and durability.

Inexpensive methods of forming spheroidal beads of adequate strength arewell-known to those skilled in this '3112.

' As previously pointed out the backing of the draw sheet or blanketmust withstand long hard usage. Accordingly fabric materials arepreferably employed. For example, straight-laid, square-woven fabricsuch as kier-boiled drills comprising 1.9.7 yards per pound has beenfound to besatisfactory. Other sheet materials, such as vulcanized orhydrolized bre, tough glass fibre sheets and certain paper which isresilient and is not permanently deformed under pressure, as paperimpregnated with rubbery ma- Iterial, may be employed. A fairly highdegree of compressibilityand resiliency is desirablein the backing ,toallow the bead-coated material as a whole to be temporarily compressedunder locally applied pressure to compensate for ordinary inequalitiesin the type face level or slight inaccuracies in the cylinder face. Thusthe backing member may comprise open-mesh fabric coated on both surfaceswith rubbery material which extends through the meshes to form a unitarymember.

It is to be understood thatthe spheroidal or globular bodiesconstituting thefacing of our improved draw sheet or blanket are hereinsometimes called beads for convenience of reference only and not tolimit the subject matter to conventional bead sizes or materials whichare designed to produce various optical or ornamental effects.

The point contact support of the material to be printed upon, affordedby our minute, hard, spherical members, has been found to reduce verymaterially, or to eliminate, first impression oiset and smearing orblurring of the first impression printing even when slippage of the weboccurs during second impression printing.

Furthermore, greatly improved printing has been obtained by employingdraw sheets or blankets of the type described in'that the improvedbeaded product possesses the proper amount of firmness or surfacehardness which results in faithful reproduction of half tones, sharpclear type areas and uniform and complete coverage of solids. Inprinting half tone dots on a paper web supported against a soft rubbertop sheet of the conventional type, the stereotype frequently forces thepaper web into the rubber and prints the side or shoulders of the halftone dots in addition to the surface portion, producing distorted dotsand a poor reproduction of the half tone. The beaded, discontinuous,planar surface of our improved top sheet accurately prints only thesurface of the stereotype since protruding portions of the stereotypecannot force the paper into the hard top sheet. Under printing pressurethe beads may be compressed into the cushioning layer without permittingthe printing of the type edges and shoulders upon the paper web. Thusdiscrepancies in the height of the stereotype, which occasionallyapproximate .006 inch error, are readily absorbed in our improvedconstruction by compressing the beads into the resilient bead bond,cushioning underlay `and backing.

lLeaders or rule lines, set in stereotypes to print couponedges ordotted lines, do not damage our improved draw sheet or permanentlyemboss it as is customary when printing against a rubber blanket or drawsheet. Our draw sheet presents a hard surface which is not cut orembossed by the sharp leaders and thus eliminates reproduction of theprevious pattern on subsequent printing with theV same draw sheet, whichis called ghosting Likewise our improved draw'sheets show no permanentembossing even after having been subjected to the compression of severalmillion printing impressions. The resiliently supported beads returnimmediately to their former planar contour after each impression and thesheet may be reused on many different printing operations. One seriousdifficulty with rubber, cork and other deformable draw sheets of the artis that after supporting a great number of printing impressions of thesame outline, this outline becomes permanently embossed on the surfaceof the sheet rendering it unusable in supporting printing impressions ofa dilferent outline, since it will subsequently ghost the prior outlineonto the paper web. Printing impressions numbering many millions havebeen made lupon our resilient, beaded draw sheets without producingobjectionable embossing.

Tests aggregating ten millions of impressions on a single beaded drawsheet in a high speed rotary newspaper press demonstrate that ourimproved dra-w sheet or blanket materially reduces or eliminates rstimpression offset., A draw sheet has been produced which for the rsttime permits printing rst impression signatures which closely approachsecond impression printing in quality. This result is achieved, rst byreason of the fact that ink adheres much less readily to glass beadsthan to rubber employed in commercial draw sheets. Secondly bypresenting a multitude of minute, hard, discontinuous surfaces, theundried ink on the web does not tend to transfer to our draw sheet whichdoes not present a continuous surface upon which small pools of ink mayform due to surface tension. The exceedingly small quantities of inkthat may be transferred to the draw sheet are forced into theinterstices between the beads and thus absorption of ink by the paperweb on subsequent impressions is avoided. A further advantage of ourdraw sheet is that it requires little or no cleaning. Somedraw sheetshave run upwardly of 41/2 million impressions without requiring washing.

As previously set forth the support or backing for the beaded draw sheetfacing, in order to perform satisfactorily on newspaper rotary or at bedpresses, where make-ready is not employed, should be sutlicientlyresilient and temporarily compressible to absorb the compression of thebeaded surface when printing from uneven stereotypes as frequentlyoccurs in printingnewsf papers. The use of our improved draw sheet isnot limited to presses which do not employ make-ready, as it also hasconsiderable utility in so-called hard pack presses which uniformlyemploy make-ready. The use of our improved draw sheet on newspaperpresses has been emphasized herein since such usage presents the mostexacting requirements of draw sheets, blankets or tympan sheets. Thesupport must also be tough, tear-resistant and relativelyfatigue-resistant to stand up under approximately million or moreprinting impressions. Accordingly a straight-laid square woven fabric ispreferably employed as the base member since it is more resistant topermanent deformation than most papers or other felted materials.

To obtain the desired resilience, a cushioning layer is preferablyinterposed between the base member and the beaded surface; or, ifdesired, it may be coated upon the outer surface of the base member. Thecushioning layer is preferably formed of elastic polymers with orwithout adhesion-inducing agents and is sul'iciently tough and resilientto resist yieldingly and absorb partially the localized, temporarydepression of the spherical beads, when subjected to printing pressure.To provide this resiliency the cushioning layer preferably has a Shorehardness of 50 to 75, although satisfactory cushioning layers may bemade with a Shore hardness varying from 3() to 90. Mixtures of syntheticand natural rubber, highly cured, provide a satisfactory cushion coat,as they adhere very well to fabric and paper backing and will not stripoff in use. Such mixtures preferably contain resins to obtain rrnadhesion to the fabric base member and to the bond for the sphericalbodies. The cushioning layer may comprise a thermosetting orthermoplastic resin or mixtures thereof, such as Vinylites, acrylates,siliconesand the like. Glue-glycerine compositions may also be used.

A highly satisfactory cushioning coat has been formed of a rubberybutadiene-acrylonitrile polymer and a phenolic adhesion-inducing agent.This cushioning composition may be formed in accordance with thefollowing formula, in which the parts are set forth by weight.

Example 1 Parts by weight Rubbery butadiene-acrylonitrile polymer 100Compatible heat-reactive phenolic resin 75 Plasticizer 17 Pigment(carbon black) 5 Variationsboth inratio and identity of monomers. `which6 produce analogous copolymers are contemplated. vFor. example, acopolymer of 55 parts of butadiene and 45' parts of methacrylonitrilehas been successfully employed in these compositions, as has a copolymerof 60 parts butadiene and 40 parts acrylonitrile.

Durez 175 resin, a product of Durez Plastics and Chemicals, Inc., NorthTonawanda, New York, is a commercially available resin which has givengood results when used in the formula of Example 1; it is soluble inmethyl ethyl ketone, insoluble in benzene, has a temporary melting pointof C., and is understood to be the reaction product obtained fromphenol, acetaldehyde and formaldehyde in the approximate molar ratio of1.0:0.25 :0.95. Another commercial resin which is equally effective isVarcum 5476 resin, a product of Varcum Chemical Corp., Niagara Falls,New York.

Dioctyl phthalate is one example of a plasticizer which has given goodresults in formulas such as that of Examples l-3; dibutyl sebacate,tributoxy ethyl phosphate, or other analogous plasticizers, may,however, be substituted therefor in whole or in part.

The cushioning layer of Example 1 may be compounded in a rubber mill.The rubbery polymer is milled for approximately 15 minutes and then theplasticizer and carbon black or other ller are slowly added. Finally,the finely crushed resin is added rapidly. The cushioning layer may beapplied to the fabric base by means of a 3-roll calender. The calenderroll temperatures, pressure and speed are adjusted to provideessentially a surface coating of the composition on the fabric, withonly minor penetration. In forming a draw sheet .026 inch thick theintermediate cushioning layer is approximately .O08 inch thick. In thisconstruction the fabric backing may be approximately .015 inch and thebeads approximately .003 inch. To obtain a thinner draw sheet ofapproximately .020 inch, such as is suitable for use on Duplex and GossComet flat bed presses, the cushioning layer may be .002 inch thick.

The cushioning layer of Example l may also be applied to the fabric by atransfer coating method in which the solution is knife-coated on acarrier web, the adhesive content is tackied by heating and the materialis then transferred to the fabric base at nip rolls. In this case thecomposition is formed by first milling the polymer and then dissolvingit in a suitable solvent such as hexone and subsequently dissolving andadding the resin content. The plasticizer and pigment, in a dispersedform, are then added and mixed thoroughly. 362 parts of hexone may beemployed with the composition shown in Example 1. After the cushioninglayer has dried the carrier web may be stripped from the fabric, whichas previously mentioned may comprise a kier-boiled drills cloth. Thecushioning layer is coated on the fabric in such manner that 24 squareinches of it weighs 60 grains, when dry, in the .026 inch thick drawsheet.

A cushioning layer having the desired resiliency and durability may alsobe prepared in accordance with the following formula.

Example 2 Parts by weight Rubbery butadiene-acrylonitrile polymer .100Compatible coumarone-indene resin l0 Zinc oxide 5 Stearic acid 1Plasticizer 10 Filler (semi reinforcing carbon black) Sulfur 1.25Primary accelerator 1 Secondary vulcanizer 0.75

The composition of Example 2 may be prepared and calendered or coated onthe backing member in the manner described in connection with Example 1.The cornposition is then heated to obtain a tight cure. Likewise .thebutadiene-acrylonitrile polymer and the plasticizer may be the same asthose described in connection with Example l. The primary acceleratormay comprise 2- mercapto benzothiazole, such as sold by the VanderbiltCompany under the trademark Captax. The secondary vulcanizer maycomprise zinc diethyl dithiocarbamate.

A satisfactory cushioning layer which does not employ anadhesion-inducing resin is shown in the following formula.

Example 3 Parts by weight Natural rubber-smoked sheets 100 Zinc oxide 5Stearic acid 1 Antioxidant Y l Filler (medium process channel black) 40Delayed accelerator 0.25 Primary accelerator 0.75 Sulfur 3 Theantioxidant may comprise phenyl alpha naphthylamine. The delayedaccelerator may be 2,2-benzothiazyl disulde. This formula may becompounded in a rubber mill as described in connection with Example land then calendered or coated upon the backing member. It is heated toobtain a tight cure.

The foregoing examples are illustrative only and other compositionshaving the desired resiliency, durometer hardness, adhesion propertiesand tensile strength will be apparent. For example a cushioning layeremploying as a basic ingredient neoprene (polychloroprene), Thiokol (asulphur-olefin resin), buna type rubbers, plasticized polyvinylchlorides, butyrals or silicone rubbers is contemplated. Likewise thetypes and proportions of resins, plasticizers, llers, vulcanizers, etc.in the foregoing examples may be modied somewhat without apprecablyaltering the desired physical properties, previously enumerated, of thecushioning layer.

The beads are secured to the cushioning layer by a tough, resilient andexible bonding composition which has a high and permanent adhesion tothe beads. It has been found that the combination of properties requiredin an adhesive suitable for bonding beads to the cushioning layer, curedon the fabric backing, in producing draw sheets or blankets adapted forthe rough usage encountered in newspaper presses, is obtainable withcertain compounds comprising elastic polymers and adhesioninducingagents. The rubbery butadiene-acrylonitrile polymer and anadhesion-inducing agent of Example 1, dissolved in an organic solvent,e. g. methyl isobutyl ketone, to a coatable viscosity, such as 14,000centipoises at room temperature, provides an excellent bondingcomposition for glass beads and has the desired resiliency to withstandtemporary deformation of the planar beaded surface under printingpressures.

The beads may be coated upon the composite backing `in accordance withmethods which have been employed in the manufacture of coated abrasivematerial. For example, the small spheres may be sprinkled or spread uponthe adhesive coated web by gravity, the excess spheres being-thenremoved. Before the adhesive has set, the coated web is passed betweenaccurately spaced nip rolls which level the tops of the spheres andsubmerge them lto the required depth in the adhesive, preferably over50% of area of the spheres. The beaded product is then ypartly cured byheating and a second or sizing coat may then be spread over the spheresin order to more firmly secure them to the flexible backing or to imparta surface which will reduce any tendency of the ink or other subfstancesencountered in a particular use to adhere to the beaded material. Thecomposition of Example l, when Vcompletely cured,V has highink-repellent properties and -may be applied as the size coating in asolution comprising -two parts of Example l and l part solvent, e. g.hexone. The sizing coating is of molecular thickness on the sur- :faceof the Abeads and may be applied `byrneans of .a f"' roll partiallyvimmersed and revolving in a pan of sizing solution and contacting withthe beaded coated surface of the web, or by spraying with a sizingsolution, or by any other suitable means. The beaded product may thenagain be passed through the spaced nip rolls and is again heated toobtain a fully cured bond. Employing the bonding composition and sizesolution of Example 1, as described, a bonding composition which has ahigh and permanent adhesion to glass beads is obtained if the partialcures and final cure is equivalent to a draft oven cure of fourteenhours at 250 F.

A bonding coating weighing eight grains (dry weight) per 24 squareinches is adequate. If, as is preferred, the cushioning layer, bead bondand size coat are formed from the composition of Example 1, it isapparent that the laminations have high cohesive values and that itwould be very dicult to strip the layers from each other. It will alsobe apparent that by employing a slightly thicker cushioning layer, theadhesive layer per se may be omitted. For example the surface of thecushioning layer may be rendered adhesive by applying a solvent thereto,the beads sprinkled on the adhesive surface; the beaded composite isthen passed through nip rolls and heat cured. This modification is notpreferred since it is dicult to obtain a substantially planar beadedsurface, as it is dicult to control accurately the degree of submergenceof the beads in the combined bonding and cushioning layer. y

Example 4 Another suitable bead bonding composition may comprise 10.parts of polychloroprene (Neoprene CG), 15 parts of compatibleoil-soluble heat-reactive phenol-aldehyde resin (Bakelite 3360), 5 partsof dioctyl phthalate, 0.5 part zinc oxide, and 0.4 part magnesium oxide,dissolved to desired viscosity in butyl acetate. This composition may becoated on the cushioning layer of the fabric, glass beads applied on thecoating in the manner described, and the composition is then dried andcured to form a tough adhesive. The bond should be cured for two hoursor more at C.

Example 5 Another composition which forms a firm and resilient bond toglass beads as well as to the cushioning layer may be prepared from amodified Buna S-type polymer and an oil-soluble reactive phenolic resin.

In this example, a rubbery copolymer of 50 parts butadiene, 40 partsstyrene and 10 parts acrylonitrile may be used with an equal weight of acompatible oil-soluble heat-advancing phenol-aldehyde resin, dissolvedin butyl acetate. The resin may be an alkali-catalyzed reaction productof orthophenyl phenol and formaldehyde, and correspond to the Bakelite3360 resin of Example 4. After coating the bond is cured by heating forat least two hours at 100 C.

In the above examples, various types of resins, cornpatible with theparticular polymers employed have been used as adhesive-inducing agentsto provide the required high adhesion to glass. Various other compatiblephenolic resins may be employed as adhesion-inducing agents and ascuring agents to provide the required degree of adhesion value andresilient properties. For example, an alkyd resin formed by reactingglycerol with a rosin-maleic anhydride adduct has provided an elfectivedegree of adhesion when combined with Hycar OR-15 polymer and aplasticizer and properly cured, as by prolonged heating in the presenceof a small amount of an urea-formaldehyde resin.

To illustrate exemplary embodiments of the invention, and not to limitit, reference is made to the accompanying drawing in which:

Figure l is an enlarged section through bead coated material madeaccording to a preferred embodiment of .the present invention;

Fig. 21isa diagrammatic section-of printing apparatus 9 employing twoprinting couples in which both sides of a paper web are printed and inwhich the impression cylinders are shown covered with material embodyingthe invention;

Fig. 3 is a fragmentary enlarged sectional view showing the action ofthe printing type on the paper web and the small globular bodies inContact with a portion of the paper web;

Fig. 4 is an enlarged sectional View of a form of invention havingparticular utility as a blanket for the impression cylinders ofnewspaper presses wherein the baci;- ing comprises laminations of fabricand rubbery elastomers; and

Fig. 5 is an enlarged sectional view of material made in accordance withthe invention and having a modified form of backing.

Referring in detail to the drawing (in the several tigures of which likereference characters denote similar parts), in Fig. l a `sheet 8 isshown in which small globular bodies 9 are secured to a cushioning layer10 by means of an adhesive 11. Thus the cushioning layer 10 isinterposed between the beads or bodies 9 and a flexible backing 12. Thebodies 9 are approximately uniformly spaced and substantially sphericalin shape. These bodies are shown submerged in the adhesive to a depthsomewhat in excess of one-half their diameters so that each ispositively confined in a strong socket wherein surface adhesion alone isnot depended upon to anchor the bodies. The film 21 of sizing is showncovering the protruding surfaces of the bodies 9 and the interveningexposed surfaces of the adhesive 11. As hereinbefore indicated, thesizing film 21 increases the bond and may be of such character to repelor minimize adherence of ink or of other substances that are to beencountered in use. Also as previously indicated, the sizing film 21 maybe omitted.

In Fig. 2 the reference character 13 indicates a paper web, which is fedin the `direction of the arrow from a supply roll (not shown) betweenthe type cylinder 14, inked by means of an ink roller 15, and the iirstimpression cylinder 16 which is preferably faced with our bead coatedmaterial 8. The paper 13, thus printed on the lower surface, is then fedbetween a second plate cylinder 17, similarly inked by an ink roller 18,and a second impression cylinder 19, faced with the improved draw sheetor blanket 8. It will be understood by those skilled in the printing artthat in conventional newspaper presses, underpacking (not shown) isdisposed between the periphery of the impression cylinder and the drawsheet or blanket. The underpacking may comprise one or two layers ofrubber or cork. The addition of wiper rolls (not shown) to wipe the drawsheet or blanket or to meisten it with a suitable ink solvent may beused.

Fig. 3 illustrates in more detail a part of the printing process withwhich this invention is particularly concerned. The paper web 13 afterit has been printed on the lower surface, is fed between a platecylinder 17, having type 20, and an impression cylinder 19, faced Withthe improved draw sheet 8. The draw sheet comprises a ilexible backing12, and a cushioning layer 10, and small solid globular bodies 9, suchas glass beads secured to the backing 12 by means of an adhesive 11. Thedraw sheet 8 is drawn tightly over underpacking 22 secured to thesurface of the impression cylinder 19.

In practice, glass spheres having a diameter in the neighborhood of .001to .005 inch, e. g., .003 inch, corresponding to No. l5 bead size and220 grit size are suitable as a facing for printing press draw sheetsand blankets, but smaller or larger sizes may be employed as desired. ifsmall solid globular bodies other than glass spheres are used, thediameter of the individual globular bodies may be as above indicated forglass spheres. The flexible backing is preferably made of cloth, and maybe sized or unsized, and of a thickness of the order of .008 to .020inch, e. g. .015 inch.

Fig. 4 shows a modified sheet in which the globular bodies 9 form thecontact facing on a composite backing which may comprise a cushioninglayer 10, a cloth layer 23, a cushioning layer of a rubbery elastomer24, a second cloth layer 25, another layer of a resilient elastomer 26,and an inner cloth layer 27. This backing is particularly suitable foruse as a blanket on the impression cylinders of newspaper presses,employing a single layer of underpacking. As previously mentioned, papermay be employed in place of one or more of the cloth layers 23, 25 and27 and the number of layers may be reduced.

The blanket is usually 0.080 to 0.092 inch thick and since the beadedsurface comprises approximately 0.003 inch, the laminated backingincluding several fabric layers interposed with layers of resilientmaterial bonded thereto calipers from 0.077 to 0.089 inch. It isapparent that by varying the thickness of the fabric and resilientlayers the number of the layers may be increased or reduced to obtain ablanket of the thickness desired.

A further modified form of backing for the beaded sheet is shown in Fig.5. In this embodiment, a cloth Vlayer 28, preferably of open mesh, isinterposed between two layers 29, 30, of resilient materials such as arubbery elastomer of the types mentioned. The fabric serves as a.reinforcement for the cushioning layers 29, 30 which preferabiypenetrate the meshes of the fabric to form a wellbonded, integralbacking. Beads 9 are bonded to the upper cushioning layer 29 by anadhesive 11 in the manner described. A rubbery material having lowstretch may be used as the cushioning layer and the cloth reinforcementmay then be omitted.

The flexible backings described provide strength combined withresiliency and a degree of compressibility. Other combinations ofcomposite backing materials as well as variations in the intermediaterubbery layers which are firmly adhered to the fabric layers, as well asvariations in the bead sizes and bonding compositions, within the scopeof our invention, will be understood from the foregoing description.

Thus the sheet having a discontinuous beaded surface supported on aresilient underlay may be manufactured in the form of a sleeve with arelatively inflexible backing. In use the bead-surfaced sleeve isslipped over the periphery of the impression cylinder and held tightlythereon by clamps or a takeup reel.

Likewise it is to be understood that the improved beaded, laminatedmaterial may be semi-permanently bonded on the periphery of theimpression cylinder. In this modification one or more layers of cork orrubber underpacking may be firmly cemented to the metal periphery of thecylinder and the beaded sheet bonded hereover.

As previously set forth, the hard, discontinuous surface, of the topsheet, contacting the freshly printed surface of the paper web, maycomprise hard rubber or a hard resin, in the form of beads or otherwise,in place of the preferred glass beads. For example, in one embodimentthe rubbery layer may be applied over a cushioning layer of the typedescribed, embossed to provide a discontinuous surface, such as minuteconvex or pyramidal protuberances, and vulcanized to a Shore durometerhardness of S5 to 100. A suitable rubbery compound adapted to bevulcanized to present a discontinuous surface of the desired degree ofhardness, is presented in the following example.

Example 6 parts butadiene-acrylonitrile copolymer 35 parts sulfur-groundor precipitated 50 parts iron oxide l5 parts plasticizer l0 partscoumarone-indene resin, M. P. 25 C.

2 parts zinc dibutyl dithiocarbamate This composition is preferablycoated upon a resilient or cushioning layer of the types of Examples l,2 and 3 in the form of a solution of the above lcompound in a suitablesolvent such as'methyl isobutyl ketone and Z-nitropropane and comprising30 percent solids. The surface 'layer may be coated .007 inch thickbefore evaporation of the solvent and iinal cure. A hard discontinuoussurface of minute proftuberances may then be formed by placing thelamination including the cushioning layer and surface layer in a pressadapted to emboss a discontinuous surface, such as la convex surface ora pyramidal surface in the rubbery layer. The surface layer and theunderlying, partially cured, cushioning layer are then cured to thedesired degree of hardness, for example for 90 minutes at 320 F.

In the above example dioctyl phthalate is a preferred plasticizer. Otherrubbery polymers may be employed, in place of butadiene-aerylonitrilepolymer, such as Buna S polymer, natural rubber and polychloroprene.Other fillers may be employed in place of iron oxide, such as carbonblacks, Whiting and preferably ebony rubber dust. Likewise compatibleresins other than the coumaroneindene resin mentioned may be employed,`as well as other suitable secondary vulcanizers. i

it will be readily apparent from the foregoing description that agreatly improved draw sheet or printing press Vblanket has beenproduced. Superior results are obtained by the use of small solidglobular, spheroidal or pyramidal bodies. They provide a uniform surfacesupported by Vstrong bonding materials, preferably submerging more thanhalf the surface of each body. Thus a surface is presented which doesnot break down under heavy usage and in which the points of contact withthe web to be printed upon are retained at a uniform elevation. AVfurther advantage, particularly important in printing presses which donot employ make-ready, is derived from the resilient cushioning layerinterposed between the beads and the backing. From the foregoingdescription it will be evident that by the use of this invention thelong standing problem of first impression offset may be materiallyreduced or eliminated.

Moreover, our improved material, by reason of its controlled surfacecharacteristics, resilient support and durability, is adapted to meetthe need for improved contact material in a great variety of otherfields of use. For example, as a printing accessory, it may be employedin a form of an endless belt in rotogravure presses employed in printingtextile material in place of the conventional grey cloth roll or belt.In such textile presses the ink or dye, applied to the textile fabric byan etched, rotogravure cylinder, penetrates the fabric. Our beadedmaterial in the form of an endless belt is trained around the supportingor impression cylinder between the cylinder and the fabric beingprinted. It picks up the ink or dye penetrating the fabric. The beltthen passes through a bath which removes thefink or dye, as part of acontinuous process. Likewise, the improved beaded material in the formof an endless belt may be used as a die Wiper material for steelengravings. The ink may be washed from the beaded surface and thematerial reused many times in place of the conventional paper wipeswhich are thrown away after each use. Our material also has considerableutility in the form of an endless belt for use on bronzing machines,which print a clear varnish and is then dusted with bronze or otherpowder.' Other uses will be readily apparent.

What we claim is:

A draw sheet or printing blanket adapted for use in preventing offset inprinting comprising a exible fabric backing, a continuous cushioninglayer of rubbery material of a Shore hardness of 50-.75 firmly bonded toone surface of said backing, said cushioning layer being tightly curedto provide a tough and resilient layer, and a surface coating of smallspheroidal bodies bonded to said cushioning layer by an adhesiveresistant to softening under printing pressure, said cushioning layerhaving a thickness of at least two-thirds the diameter of saidspheroidal bodies.

References Cited in the file of this patent UNITED STATES PATENTS687,711 Allen Dec. 3, 1901 705,294 Rhodes July 22, 1902 823,445 SchrammJune 12, 1906 1,492,123 Decker Apr. 29, 1924 1,947,986 Harley Feb. 20,1934 2,014,043 Harbinson et al. Sept. 10, 1935 2,073,918 Benner Mar. 16,1937 2,076,376 Lewis et al. Apr. 6, 1937 2,143,946 Hunter Jan. 17, 19392,153,755 Higgins Apr. 11, 1939 2,271,125 Juve Jan. 27, 1942 2,354,018Heltzer July 18, 1944 2,354,048 Palmquist July 18, 1944 2,354,049Palmquist July 18, 1944 72,379,741 Palmquist July 3, 1945 2,403,752Phillippi July 9, 1946 2,407,680 Palmquist Sept. 17, 1946 2,430,534-R0dli NOV. 11, 1947 2,489,791 Liles et al. Nov. 29, 1949 2,555,319Cross June 5, 1951 VOTHER REFERENCES Dubois: Plastics. Revised edition,1943. American Technical Society, Chicago, page 435. Only page 316relied on.

